I am originally from rural western Iowa, outside of Onawa, IA. I received a B.S. double major in mathematics and physics from the University of South Dakota, a M.S. in mathematics from the University of New Hampshire and a Ph.D. in mathematics from the University of Nebraska-Lincoln. My specialization is in the area referred to as Feynman's operational calculus, an area of mathematics closely related to quantum mechanics and quantum electrodynamics which was originated by R. P. Feynman in approximately 1950.
Teaching Interests
Feynman's operational calculus
Research Focus
Feynman's operational calculus, complex dimensions and fractal strings.
Blending Instantaneous and Continuous Phenomena in Feynman’s Operational Calculus with G. W. Johnson, in “Stochastic Analysis and Mathematical Physics (SAMP/ANESTOC 2002) Proceedings of the Mathematical Legacy of R. P. Feynman”, World Scientific, Sept. 2004.
Oxford University Press Noncommutativity and Time-Ordering: Feynman’s Operational Calculus and Beyond, with Michel Lapidus and G. W. Johnson, published by Oxford University Press, in print September 2015.
Articles
Integral Equations and Operator Theory Lance Nielsen, The abstract approach to Feynman's operational calculus using arbitrary time-ordering measures is developed using two approaches to addressing the combinatorial complexities which arise. An evolution equation is established for the second of the two approaches and examples are considered. 94, Issue 2, Article Number 15 2022
New York Journal of Mathematics Nielsen, Lance A distributional approach to Feynman's operational calculus 20, p. 377-398 2014
New York Journal of Mathematics A Distributional Approach to Feynman’s Operational Calculus, New York J. of Math. 20 (2014), 1-22. 2014, p. 1-22 2014
Journal of Doctoral Nursing Practice Towards a Comprehensive Stability Theory for Feynman’s Operational Calculus: The Time Independent Setting, Acta Appl. Math., 2014, in press. DOI 10.1007/s10440-014-9957-1. 2014 2014
Journal of Fuzzy Mathematics Fuzzy Cores in Spatial Models, J. of Fuzzy Mathematics, Vol. 21, No. 4, 2013. 21, 4 2013
Mathematical Physics, Analysis and Geometry Nielsen, Lance Weak Convergence and Banach Space-Valued Functions: Improving the Stability Theory of Feynman's Operational Calculi 14, p. 279-294 2011
Mathematical Physics, Analysis and Geometry Weak Convergence and Banach Space-Valued Functions: Improving the Stability Theory of Feynman’s Operational Calculi, Math. Phys. Anal. Geom. 14 (2011), 279-294. 14, 2014 2011
Acta Applicandae Mathematicae Nielsen, Lance Feynman's Operational Calculi: Disentangling Away from the Origin 110, p. 409-429 2010
Critical Review Clark, T. D., Mordeson, J. N., Nielsen, L., Wierman, M. J. Fuzzy geometry: applied to comparative politics 2, p. 1-12 2008
Mathematical Physics, Analysis and Geometry Nielsen, L. Weak convergence and vector-valued functions: Improving the stability theory of feynman's operational calculi 10, p. 271-295 2007
Mathematical Physics, Analysis and Geometry Jefferies, B., Johnson, G. W., Nielsen, L. Feynman's operational calculi: Spectral theory for noncommuting self-adjoint operators 10, p. 65-80 2007
Acta Applicandae Mathematicae Nielsen, L. Stability properties for feynman's operational calculus in the combined continuous/discrete setting 88, p. 47-79 2005
Rocky Mountain Journal of Mathematics Nielsen, L. Time dependent stability for Feynman's operational calculus 35, p. 1347-1368 2005
Journal of the Korean Mathematical Society Feynman’s Operational Calculi for Time Dependent Noncommuting Operators, with Brian Jefferies and G. W. Johnson, J. Korean Math. Soc. 38 (2001), 193 – 226 38, 2001, p. 193-226
Conference Proceedings, Canadian Mathematical Society A Stability Theorem for Feynman’s Operational Calculus, with G. W. Johnson, Conference Proc., Canadian Mathematical Society, 29 (2000), 351 – 365 29, 2000, p. 351-365
Proceedings of the American Mathematical Society Effects of Absolute Continuity in Feynman’s Operational Calculus, Proc. Amer. Math. Soc. 131 (2003), 781-791 131, 2003, p. 781-791
Acta Applicandae Mathematicae Stability Properties of Feynman’s Operational Calculus for Exponential Functions of Noncommuting Operators, Acta Applicandae Mathematicae 74, 2002, 265 – 292 74, 2002, p. 265-292
Rocky Mountain Journal of Mathematics Time Dependent Stability for Feynman’s Operational Calculus, Rocky Mountain Journal of Mathematics 35 no. 4 (2005), 1347 - 1368 4, 2005, p. 1347-1368
Acta Applicandae Mathematicae Stability Properties for Feynman’s Operational Calculus in the Combined Continuous/Discrete Setting, Acta Applicandae Mathematicae 88 (2005), 47 – 79. 88, 2005, p. 47-79
Mathematical Physics, Analysis and Geometry Feynman’s Operational Calculi: Spectral Theory for Noncommuting Self – Adjoint Operators, with B. Jefferies and G. W. Johnson, Mathematical Physics, Analysis, and Geometry, 10 (2007), 65 - 80 10, 2007, p. 65-80
Mathematical Physics, Analysis and Geometry Weak Convergence and Vector-Valued Functions: Improving the Stability Theory of Feynman’s Operational Calculi, Mathematical Physics, Analysis, and Geometry, 10 (2007), 271 - 295. 10, 2007, p. 271-295
Integration: Mathematical Theory and Applications An Integral Equation for Feynman’s Operational Calculus, Integration: Mathematical Theory and Applications, Volume 1, Number 1, 2008, pp. 49 - 66. 1, 2008, p. 49-66
Acta Applicandae Mathematicae Feynman’s Operational Calculi: Disentangling Away from the Origin, Acta Applicandae Mathematicae ,110 (2010), 409-429. 110, 2010, p. 409-429
New York Journal of Mathematics á Feynman’s Operational Calculus : Using Cauchy’s Integral Formula, New York J. of Math. (16) 2010, 1 - 26. 16, 2010, p. 1-26
Mathematical Physics, Analysis and Geometry Weak Convergence and Banach Space-Valued Functions: Improving the Stability Theory of Feynman’s Operational Calculi, Math. Phys. Anal. Geom. 14 (2011), 279-294. 14, 2011, p. 279-294
New York Journal of Mathematics A Distributional Approach to Feynman’s Operational Calculus, New York J. of Math. 20 (2014), 1-22. 20, 2014, p. 1-22
Acta Applicandae Mathematicae Towards a Comprehensive Stability Theory for Feynman’s Operational Calculus: The Time Independent Setting, Acta Appl. Math., 138 (2015), 59-79. 138, 2015, p. 59-79
Acta Applicandae Mathematicae Towards a Comprehensive Stability Theory for Feynman’s Operational Calculus: The Time-Dependent Setting, submitted for publication, July 30, 2015. 152 (2017), p. 1-31
Integral Equations and Operator Theory Combining Continuous and Discrete Phenomena for Feynman’s Operational Calculus in the Presence of a (C0) Semigroup and Feynman-Kac Formulas with Lebesgue-Stieltjes Measures Nielsen, L. Integr. Equ. Oper. Theory (2018) 90: 12. https://doi.org/10.1007/s00020-018-2428-8
New York Journal of Mathematics "Two Approaches to the Use of Unbounded Operators in Feynman's Operational Calculus"
Editing and Reviews
Analytic Tools for Feynman Integrals, by Vladimir Smirnov, Springer Tracts in Modern Physics 250, Springer, 2012. (Monograph) 2012
Presentations
Invited lecture at the South Dakota State University department of mathematics seminar. Title: "Essential Ideas and Properties of Feynman's Operational Calculus." 2018
Presented the invited talk "Feynman's Operational Calculus: Background and Esential Properties" at the spring 2017 Nebraska-Iowa Functional Analysis Seminar at Creighton University. 2017
Presented the talk: "Combining Continuous and Discrete Phenomena in Feynman's Operational Calcuus in the Presence of a (C_0) Semigroup: Feynman-Kac Formulas with Lebesgue-Stieltjes Measures" at the Joint Meetings of the AMS in Atlanta, GA. 2017
Presented the talk "An Evolution Equation for Feynman's Operational Calculus in the Combined Continuous/Discrete Setting" at the Joint Meetings of the AMS in Seattle, WA, Jan. 2016. 2016
Presented the talk: "An Evolution Equation for Feynmans Operational Calculus in the Combined Continuous/Discrete Setting" at the Joint Mathematics Meetings, Jan. 2016, in Seattle, WA 2016
Presented the invited talk "Towards a Comprehensive Stability Theory for Feynmans Operational Calculus: The Time Independent Setting" during the special session "AMS Special Session on Advances in Analysis and PDEs" at the Joint Meetings of the American Mathematical Society in Baltimore, Jan. 2014. 2014
Presented three lectures at the functional integration seminar at the University of Nebraska, Lincoln, fall 2012. 2012
Presented three lectures at the functional integration seminar at the University of Nebraska, Lincoln, spring 2012. 2012
Presented the contributed talk "Feynmans Operational Calculus: Using Cauchys Integral Formula" at the Joint Meetings of the AMS, Boston, January 2012. 2012
Presented the contributed talk "Feynmans Operational Calculus: Using Cauchys Integral Formula" at the Joint Meetings of the AMS, Boston, January 2012. 2012
Presented three lectures at the functional integration seminar at the University of Nebraska, Lincoln, fall 2011. 2011
Presented the invited talk "Feynmans Operational Calculus: Background and a Survey of Current Research" at the University of Nebraska, Omaha, April 22, 2011 2011
Presented two lectures at the functional integration seminar at the University of Nebrask, Lincoln, spring 2011. 2011
Presented two lectures at the functional integration seminar at the University of Nebraska, Lincoln, fall 2010. 2010
Presented three lectures at the functional integration seminar at the University of Nebraska, Lincoln, spring 2010. 2010
Presented "Feynman's Operational Calculus Beyond an Introduction" at the University of California, Riverside, March 2009. 2009
Presented 4 lectures on current research at the Functional Integration Seminar at UNL, Fall 2008. 2008
Presented "Weak Convergence and Vector-Valued Functions: Improving the Stability Theory of Feynman's Operational Calculus" at the Joint Meetings of the AMS, Jan. 2008 2008
Presented 5 lectures at the Functional Integration Seminar at UNL in Fall 2007. 2007
Presented 6 lectures at the Functional Integration Seminar, Spring 2007. 2007
Presented 5 lectures on current research at the Functional Integration Seminar at UNL in Spring 2006. 2006
Presented "An Integral Equation for Feynman's Operational Calculus" at "The Feynman Integral and Related Topics in Mathematics and Physics" at UNL in 2006. 2006
Presented 5 lectures on current research at the Functional Integration Seminar at UNL, spring 2005. 2005
Presented "An Integral Equation for Feynman's Operational Calculus" at the Joint Meetings of the AMS, Jan. 2005. 2005
Presented 8 lectures on current research at the Functional Integration Seminar at UNL in Fall 2004 2004
Eight lectures on on-going research at the Functional Integration Seminar at UNL in the fall of 2004 2004
Presented 5 lectures on current research at the Functional Integration Seminar at UNL in Spring 2003. 2003
Invited Lecture - "A Survey of Feynman's Operational Calculus" at the Nebraska Iowa Functional Analysis Seminar, April 2003. 2003
Presented "Blending Instantaneous and Continuous Phenomena in Feynman's Operational Calclus" at the Joint Meetings of the AMS, Jan. 2003 2003
Presented 8 lectures on current research at the Functional Integration Seminar during the Fall of 2002. 2002
Presented 6 lectures on current research at the Functional Integration Seminar at UNL in the Spring of 2001 2001
Presented "Effects of Absolute Continuity in Feynman's Operational Calculus" at the Joint Meetings of the AMS, January 2001. 2001
Presented 6 lectures on current research at the Functional Integration Seminar at UNL during the Fall of 2000. 2000
Presented "Stability Properties for Feynman's Operational Calculus" at the International Conference on Feynman Integrals and Related Topics. 1999
Presented the invited lecture "Feynmans Operational Calculi : Background and a Survey of Current Research" at the Nebraska - Iowa Functional Analysis Seminar in Des Moines, IA
Presented the invited talk "An Integral Equation for Feynmans Operational Calculi" at "The 10th International Conference on Path Integrals" held at Howard University, Washington, D.C.
Presented the invited talk "Towards a Comprehensive Stability Theory for Feynmans Operational Calculus: The Time Independent Setting" during the special session "AMS Special Session on Advances in Analysis and PDEs" at the Joint Meetings of the American Mathematical Society in Baltimore, Jan. 2014.
Presented the talk: "Towards a Comprehensive Stability Theory for Feynmans Operational Calculus: The Time Independent and the Time-Dependent Settings" at the Joint Mathematics Meetings, Jan. 2015, in San Antonio.